mills



Obt. 213.1924.

R. VAN A MILLS METHOD or AND APPARATUS FOR PROTECTING METAL TANKS AGAINST CORROSION Filed June 16 1924 2 Sheets-Shae! l F1 I I I 'l 1 ,1 I I I I I /9 /7 Oct. 21 1924. 1,512,557

R. VAN A. MILLS METHOD OFAND APPARATUS FOR PROTECTING METAL TANKS AGAINST CORROSION Filed June 16. 1924 2 Sheets-Sheet 2 Qwuentoz Patented '0. 21, 1924.

UNITED STATES I 1,512,557 PATENT OFFICE.

RONALDVAN AUK EN MILLS, OFSANDY SPRING, MARYLAND, ABBIGNOB NYCE, 0! WASHINGTON,' DISTRICT OF COLUMBIA.

TO PETER Q.

Application filed June 1-8; 1924. Serial No. 720,379.

To all whom it may concern:

Be it known that I, RONALD VAN AUKEN MILLS, a citizen of the United, States of America, residing at Sandy Spring, in the county of Montgomery and State of Maryland, have invented certain new and useful Improvements in Methods of and Apparatus for Protecting Metal Tanks Against Corrosion, of which the following is a. specification.

This invention relates to a method and.

apparatus for preventing corrosion of metal tanks and other apparatus, and is particularly designed for use .in connection with oil field tanks, in which the loss due to corrosion is very great on account of the .highly destructive action of salt water which in most instances is present with the oil.

It is well known that corrosion is an electrochemical process, and that the principles involved are similar to those involved in a galvanic cell or battery. If two pieces of metal, or two areas on the same piece of metal have different electrical potential with respect to each other, or if one is electropositive with respect to the other when immersed'in an electrolyte solution such as salt water, the electro-positive metal, area, or surface (that surface from which a currentpasses from the metal to the electrolyte) will sufl'er corrosion. lln other words, corrosion always takes place on the surface of the positive element.

lit has been found that saline waters and waters containing acids of various sorts have a very great corrosive action onordinary iron or steel tanks or other apparatus. Gases such as (it), and la -LS when absorbed in water exert a very deleterious corrosive edect.

The prevention of corrosion in oil fields is particularly urgent, the damage and financial loss from it being almost beyond estimate. Oil isusually accompanied by salt water which settles to the bottoms of the tanks or other containers, used to receive and store the oil and to separate the water aptive in attacking the oil-field tanks. Magnesium chloride is a common constituent of oil-field brines and is of such a character as to be readily hydrolyzed with the liberatron of hydrochloric acid, which corrodes the steel. Furthermore, the ferrous products of corrosion themselves hasten the corroding action, because these products of corrosion are electrochemically negative with respect to iron, and set up new galvanic couples with the surfaces of the tank on which the products of corrosion accumulate.

With these principles in mind, it is the purpose of the present invention to supply a positive electrode in an apparatus so constructed as to give this positive electrode its maximum eiiiciency in protecting the METHOD OF APPARATUS FOR PROTECTING METAL TANKS AGAINST CORROSION- I metal of which the tank or other container able when corrosion. of the protecting positive electrode has taken place to such an extent as to render it unfit for further service. Furthermore, some means of preventing the deposition of bottom settlings (sediment containing products of corrosion) upon the protecting electrode and upon the bottom of the tank should be prov1ded,in order to protect the tank and lengthen the period of usefulness of the protecting electrode.

Among the common metals which are electro-positive with respect to iron may be mentioned, zinc and aluminum. Of these, zinc is preferred for the present process, and apparatus, as itis cheaply obtained, easily worked, and is in other respects particularly adapted to the present embodiment of the invention. Under certain circumstances aluminum may be used but in the further discussion of the invention zinc will be referred to as the protecting metal.

It is recognized that the protection of iron and steel against corrosion by the use of an electro-positive metal in a galvanic circuit with the iron or steel to be protected is not broadly new.

For example, zinc plates have been laced in direct metallic contact with iron an steel in order to protect the latter against corrosion This method possesses several disadvantages. First, the protection is localized,

' only the surface in the immediate vicinity of the zinc being protected. Secondly, short circuiting or cont-act action takes place between the iron and zinc, which gives rise to the rapid consumption of the zinc. Further-. more, the zinc, if uncovered, collects products of corrosion, which products of corrosion stimulate the further corrosion and consumption of the zinc.

The well known art of galvanizing iron is another method of protecting iron and steel against corrosion, and operates on the general principles involved in the protection of iron and steel by means of a metal that is electro-positive with respect to iron and steel as outlined above.

The disadvantages of galvanizing iron and steel as a method of protecting against.

- and stimulates the rapid consumption of the zinc.

Galvanizing forms a good protection against atmospheric corrosion under some conditions, but does not protect against brine corrosion, or even against atmospheric corrosion where salt vapors are present in the air, as is the case in the neighborhood of large bodies of salt water. I also recognize that the use of galvanic couples for the prevention of incrustation of boilers is old, but this process is the reverse of that employed in the present invention, and tends to stimulate the corrosion of iron. The reason for this is that the metal introduced for the collection of the scale, and to protect the iron against incrustation is electro-negative with respect to the iron. The scale therefore deposits upon the electro-negative surface, but at the same time the iron is corroded because it is electropositive with respect to the metal supplied to collect the scale.

I eliminate the disadvantage of prior methods :--(l% By using insulating spacers between the e ectro-positive zinc p ates and the surfaces to be protected. In this manner, I prevent short circuiting between the zinc and the surfaces to be protected. (2 By electrically connecting the zinc to the tank or other metal container by supplying a metallic connection preferably a wire or metal rod, from the zinc to a point on the metal tank! or other container above the water level without intermediate connection A or short circuiting. This completes a galvanic circuit and renders all of the surface of the protected metal electro-negative with respect to the zinc. By this method the consumption of the zinc is greatly reduced because the short circuitings are avoided, and the resistance in the galvanic system is increased enough to reduce current that would otherwise flow. (3) The .zinc as well as the tank bottom may be protected against the corrosive action of bottom settlings by means of a super-imposed cover of canvas or other tightly woven material which permits the passage of the electric current, but does not permit the bottom settlings to collect upon the surface f the zinc, and tank bottom. (4) The zinc is reinforced by wire netting about which the zinc plate is cast. The advantages of this construction are two-fold. First, the netting serves as a reinforcing element, as in reinforced concrete, and prevents the mechanical disintegration of the zinc, which might give rise to short circuiting. Second, the netting maintains a 00d electrical contact between the zinc an the wire by which the galvanic circuit is completed.

Havin thus described the principles upon which t e invention is based, and the method of operation, a clearer understanding of the invention may be had by reference to the accompanying drawings in which are shown illustrative embodiments of the invention.

In the drawings Fig. 1 represents an oil tank provided with a plurality of the tank protecting zinc plates.

Fig. 2 is a detailed vertical section showing a. preferred form of the protecting plate.

Fig. 3 is a top plan view of the same.

Fig; 4 is a View showing a plurality of the protecting elements connected together.

Fig. 5 is a view showin another arrangement of the protecting ements.

Fig. 6 is a plan view showing a tank bottom tted with a sectional protectin plate of zinc which completely covers the ottom surface of the tank.

Fig. 7 is a sectional view of the arrangement shown in Fig. 6.

Fig. 8 is a view showing a modified arrangement in which the protecting element is suspended at the side of the tank, and

Fig. 9 is a fragmentary view of a modification similar to Fig. 1, in which the wires which complete the galvanic circuit are connected to the oil tank above the surface of thle water, but below the top surface of the o1 Referring particularly to the arrangement shown in Figs. 1, 2 and 3, the reference numeral 10 denotes a metal tank, preferably of iron or steel, which is to be protected against corrosion. As shown, the tank contains oil as indicated at 11 and below the oil is a layer of water 12 which contains corrosive salts.

t ll

Bill

To protect the tank against local galvanic action, posed o a metal such as zinc w ich is electropositive toward iron, are provided. In order to avoid direct contact between the plates 13 and bottom 14 of the tank spacers 15 are provided. These spacers are of'any suitable insulating material as glass, porcelain, bakelite, or the like, and ma screwed directly into the zinc late as s own in Figs. 6 and 7 or may secured to Wooden frames or racks 16 as indicated in Figs. 2' and 3. As shown in Figs. 2 and 3,

a plurality of these racks are provided,

being connected by cross members 17 of any desired number. The plates 13 ma be slid edgewise into the racks as indicate in Fig. 2 and may be held in position by means of one or more. pins 18 which may be passed throu h alined apertures in the zinc plate and t e wooden frame The plates 13 are preferably reinforced by means of a wire netting 19 which is formed Within the zinc during casting. lhe circuit is completed by means of wires 20 leading from the netting to a point 21 above the surface of the water where a tap connection through the tank wall is provided. If desired the tap connection may be pro vided below the surface of the oil as indlcated in Fig. 9, so that no part of the wire is in contact with the air, the oil forming a rotective covering'for the wire.

n order to prevent the deposit of bottom sediment or products of corrosion upon the zinc plums l8, and the bottom of the tank 14, a protective covering 22 of canvas or the like may be provided, which will permit the passage of electric current to the plate, but will exclude the'corrosion products.

Any desired number of the plates may be used, and in any suitable arranement. For a it in Fig. 4 an intermeiate plate 18 suspended between two side plates by means of hooks 22 which are supported in the adacent plates.

n Fig. 5 a plurality of zincplates are located at convenient intervals, over the bottom of the ta. lln the arrangement shown in Figs. 6 and 7, a superimposed ZllLlC bottom is provided which consists of a plurality of sections which approximately cover the whole bottom of the tank. As shown, the insulators 15 are in this instance screwed directly into the zinc late itself, no wooden frame being used. tors are placed on both top and bottom surfaces of the zinc so that either surface may be placed down in the tank. A canvas cover may be placed over the zinc plates to protect them against the accumulation and stimulative action of settlings.

In the arrangement shown in Fig. 8, a

protecting elements or lates 13 comreferably, the insulazinc plate is suspended at the side of'a tank from which said plate is insulated by means of the spacers 15. A metal hook '25 serves to comp etc the galvanic circuit.

The 0 ration of these devices has been previous y set forth and will be evident rom case, the surface to be protected is'rendered electro-negative with respect to the electropositive protecting plate.

Galvanic current flows from the positive late to the negative surface asindicated y the arrows in Fig. 1, and local galvanic action on the negative plate is eliminated or materially reduced. In this manner, the life of the tank is lengthened giving a, material saving in repairs and replacement of oil field apparatus.

The protecting plates will serve for a considerable period of time, due to the fact that they are not in direct contact with the surface to be protected, and are reinforced by wire netting. When the usefulness of the protecting latcs is finally at an end, the plates may e removed and replaced at a relativel small cost.

Obvious y, many modifications Within the scope of the invention will be evident from the foregoin description and I do not wish to be limits to the details which have been outlined for the purpose of illustration.

l/Vhat ll claim is 1. A method of protecting metal tanks against the action of corrosive liquids, which consists in immersing in said liquid a metal plate which is electropositive with respect to the tank, the flat surface of said, late being in close proximity to said tank, ut s aced therefrom by means of suitable insu ators interposed between the tankand said flat surface, whereby short circuiting between said plate and tank is prevented, said plate being electrically connected to said tank by means of suitable conductors, whereby an electrical circuit is completed.

2. A method of protecting tanks composed of ferrous material against the action of corrosive liquids which consists in immersing in said liquid a zinc plate having a fiat surface in close proximity to said tank, but separated therefrom by means of suitable insulating spacers interposed between said tank and said late, whereby short circuiting between said tank and plate is prevented, said plate being electrically connected to said tank by means of suitable conductors, where by an electrical circuit is completed.

3. A device for protecting metal oil tanks against the corrosive action of the saline liquids which settle out from the oil, comprising a protective plate, which is electropositive with respect to the material of which the tank is composed, and is separated from said tank by insulating spacers interposed between said plate and the bottom of the tank, a sheet of wire netting cast within the protecting plate, and wires connectin said plate with the tank above the level the saline liquid in said tank.

4. A device for protecting .iron or steel tanks against corrosive li uids, which comprises a rotective zinc p ate immersed in the liqui insulating spacers interposed between said plates and the tank bottom, a

reinforcing member for said plate comprising a sheet of wire netting cast within the zinc plate, wires secured to said gauze and connected to the tank above the level'of the corrosive liquid, whereby a galvanic circuit is completed, and a canvas cover for protecting said plate and the tank bottom against the deposit of bottom settlings.

5. A method of protecting oil field tanks composed of iron or steel against the action of corrosive liquids which separate out from the oil, said method consisting in immersing a reinforced zinc plate in the corrosive liquid at the bottom of the tank below the oil level, said plate being in close proximity to the tank bottom but separated therefrom by means of insulating spacing members, and connected by means of wires to a portion of the tank above the level of the corrosive liquid, whereby a galvanic circuit is completed without short circuiting.

6. A device for protecting oil field tanks composed of iron or steel against the action of corrosive liquids which settle out from the oil at the bottom of the tank, comprisin a protective reinforced zinc plate immers in the corrosive liquid below the oil level and in close proximity to the tank bottom but spaced therefrom, insulating spacers interposed between said plate and the tank bottom, a sheet of wire netting cast within the zinc plate, wires connecting said plate to the tank above the level of the corrosive liq uid in the tank, whereby a galvanic circuit is completed without short circuiting, and

means for protecting said zinc plate and the tank bottom against the deposit of bottom settlings,

7. A device for protecting oil field tanks composed of iron or steel against the action of corrosive liquids which separate out from the oil, which comprises a protective zinc plate, reinforced by means of wire nettin cast in the metal, said late bein immerse in the corrosive liquid elow the level of the oil and in close proximity to the bottom of the tank, but spaced therefrom, a frame for holding said plate, insulating spacers secured to said frame and adapted to rest upon the bottom of the tank, wires connecting said zinc plate to the metal tank above the level of the corrosive liquid therein, whereby a galvanic circuit is completed without short circuiting, and a cover extending over the top of said frame for protecting the zinc plate against the deposit of bottom settlin 8. A device for rotecting metal tan against the action 0 corrosive liquids, com prising a protective plate placed below the water eve and which is electro ositive with respect to the material of whic the tank is composed, insulating spacers interposed between said plate and said tank and electrical conductors connecting said plate with the tank above the level of the corrosive liquid in the tank.

9. A method of protecting tanks composed of ferrous material against the action of corrosive liquids which consists in immersing a zinc plate in the corrosive liquid at the bottom of the tank, the flat surface of said plate being in close proximity to said tank but spaced therefrom by suitable insulating means, and said late being electrically connected to the wal of the tank above the level of the corrosive liquid.

In testimony whereof I aiiix my si ature.

RONALD VAN AUKEN M LLS. 

